1. Field of the Invention
The present invention relates to a structure for the lower portion of an automotive vehicle body, and, more particularly, to a lower body structure for an automotive vehicle in which a seat is installed above an engine disposed above and below a floor of a vehicle compartment.
2. Description of Related Art
Automotive vehicles which have engines located under passenger's compartments are classified as a "cab-over type." For a vehicle body for such a cab-over type of automotive vehicle, an access opening or hole is provided for an access to an engine for maintenance and servicing. This access opening or hole is covered and concealed by a seat mount platform, elevated from a floor, on which a seat is mounted. This seat mount platform is connected to the floor panel by means of a hinge means so as to turn up and down about a pivot axis of the hinge means , thereby opening and closing the access opening or hole. Such lower body structures are known from, for example, Japanese Unexamined Utility Model Publications Nos. 56-48961 and 61-97078.
With the lower body structure described in the above mentioned publication, because the seat mount platform is elevated upward from the floor, the structural rigidity is not always sufficient. The seat mount platform with an insufficient structural rigidity is often subjected to vibrations. In addition, a hinge means, only by means of which the seat mount platform is supported when it is turned upward so as to open the access hole, is insufficient to carry a large load including the weight of a seat and the floor is subjected to a large load through the hinge means. Further, when a great deal of energy is applied backward to the seat during, for instance, applying abrupt braking, there is a fear that the seat mount platform is forced to turn upward or be broken.
If a center tunnel is formed with an opening or hole for access to an engine from the back for engine servicing, structural rigidity is decreased, and, hence, the structural rigidity of a vehicle body is adversely affected, in particular, in close proximity of each center pillar. This is because, the center tunnel is essentially provided in order to provide an increased rigidity of vehicle body.